How to change transmission fluid on 98 nissan frontier?

Possible causes Faulty Automatic Transmission Fluid (ATF) Pressure Switch 1 Automatic Transmission Fluid (ATF) Pressure Switch 1 harness is open or shorted Automatic Transmission Fluid (ATF) Pressure Switch 1 circuit poor electrical connection

http://pdf.textfiles.com/manuals/AUTOMOBILE/NISSAN/frontier/2007_Frontier/at.pdf

see pg 160 on the above link

Your transmission is obviously failing, but it may be something as simple as low fluid level or the need for a standard transmission service. Has the fluid and filter been changed in the past 50,000 miles? If not, START THERE. It may be too late to save the transmission but there is always a chance you may.

Nothing serious, but it should probably be changed out. The ATF would dilute the gear oil. A few ounces would not matter, but a quart would not be good.

Go to this LINK to see location, the truck is a 05 but the location is the same on your truck.

I recently tried the DIY service and repair manuals from a website and it actually helped me repair transmission problem in my jcb 3cx site-master. It would'nt move forward or reverse, engine was good both solenoids for forward and reverse worked, but still couldn't diagnose the problem.
I don't have much technical knowledge but I just followed it step-wise, and now it works perfect! covers wiring, codes, diagrams, torque specs, PCV, everything
got it from www.reliable-store.com

your radiator coolant might be leaking into transmission . big recall on 05 frontier models. check to see if transmission fluid is a milky color.

power steering flush antifreese flush brake fluid flush check pads thickness replace belts oil change change transmission fluid check ac charge and check for fluid leaks check the timing replace timing belt check lights check the shocks struts check tire pressure and thickness

Check the fluid level of the transmission. Also if you haven't done so in the last 30k miles change the transmission filter/fluid and pan gasket.

From Nissan Frontier Owners Manual:
For Automatic Transmission Fluid, refill with Nissan Matic D

More details HERE

Hope helped (remember rated this help). Good luck.

i think the trans is every 60,000 and the front and rear gear oil may be at the same time...refer to the owners manual